Computer Assisted Design (CAD) and Computer Assisted Manufacturing (CAM) systems have been used for some time in the aircraft and automotive industries to design and manufacture aerodynamic and mechanical components. Such systems typically comprise a main frame computer, large bulk memory systems including tape units, rigid disk units and removable disk pack units, high resolution All Points Addressable (APA) Cathode Ray Tube (CRT) displays, a large Random Access Memory (RAM) of sufficient capacity to store the graphics application and address each pixel of the high resolution displays, and Input/Output (I/O) devices such as digitizer pads with cursors and plotters. These systems are very expensive, but their cost can could be justified because of the large sums of money invested in the design and manufacture of an aircraft or a new automobile model. The price of CAD systems has come down significantly over the past decade due to economies of computer and memory system manufacture, and because of that, CAD systems are being applied to many new uses among which are architectual design and the layout of photoresist patterns for integrated circuits. Nevertheless, CAD systems are still quite expensive, and their use is generally limited to correspondingly expensive applications.
At the other end of the spectrum are the so-called personal computers based on the microprocessors which have been developed over the past decade. These typically comprise a mother board containing the microporcessor, a Read Only Memory (ROM) encoded with the Basic Input/Output system (BIOS) for controlling the microporcessor, a limited amount of RAM, and a number of adapters for interfacing with various I/O devices. These I/O devices may include a keyboard, a medium or high resolution CRT display, one or more floppy disk drives, and a printer such as one of the more popular dot matrix printers. Although personal computers are small and compact, they are capable of some fairly sophisticated applications. They are especially well suited to business applications such as accounting, data base management and business analysis. Recently, a number of business applications have been developed which include graphics support. These applications take the input or calculated numerical data and produce line graphs, bar charts and pie charts which are much easier to interpret than the raw numerical data. Prints of these graphical displays are made by reading out the data in the APA display RAM to a dot matrix printer provided with a graphical capability or to an inexpensive pen plotter. The latter device is also capable of generating transparencies for use in overhead projectors. The acceptance of business applications with graphics support has been immediate and substantial with the result that there is a considerable demand for graphics applications which are not necessarily limited to business graphs. The ability to generate schematic diagrams, flow charts, floor plans and similar graphic displays would be highly desirable in the production of technical manuals, advertising layouts and the like.